Aniline colors are usually employed as the tinting agents. The following is a typical formula, the product being a black ink:
| I.— | Nigrosin | 3 parts |
|---|---|---|
| Water | 15 parts | |
| Alcohol | 15 parts | |
| Glycerine | 70 parts |
Dissolve the nigrosin in the alcohol, add the glycerine previously mixed with the water, and rub well together.
Nigrosin is a term applied to several compounds of the same series which differ in solubility. In the place of these compounds it is probable that a mixture would answer to produce black as suggested by Hans Wilder for making writing ink. His formula for the mixture is:
| II.— | Methyl violet | 3 parts |
|---|---|---|
| Bengal green | 5 parts | |
| Bismarck green | 4 parts |
A quantity of this mixture should be taken equivalent to the amount of nigrosin directed. These colors are freely soluble in water, and yield a deep greenish-black solution.
The aniline compound known as brilliant green answers in place of Bengal green. As to the permanency of color of this or any aniline ink, no guarantee is offered. There are comparatively few coloring substances that can be considered permanent even in a qualified sense. Among these, charcoal takes a foremost place. Lampblack remains indefinitely unaltered. This, ground very finely with glycerine, would yield an ink which would perhaps prove serviceable in stamping; but it would be liable to rub off to a greater extent than soluble colors which penetrate the paper more or less. Perhaps castor oil would prove a better vehicle for insoluble coloring matters. Almost any aniline color may be substituted for nigrosin in the foregoing formula, and blue, green, red, purple, and other inks obtained. Insoluble pigments might also be made to answer as suggested for lampblack.
The following is said to be a cushion that will give color permanently. It consists of a box filled with an elastic composition, saturated with a suitable color. The cushion fulfils its purpose for years without being renewed, always contains sufficient moisture, which is drawn from the atmosphere, and continues to act as a color stamp cushion so long as a remnant of the mass or composition remains in the box or receptacle. This cushion or pad is too soft to be self-supporting, but should be held in a low, flat pan, and have a permanent cloth cover.
III.—The composition consists preferably of 1 part gelatin, 1 part water, 6 parts glycerine, and 6 parts coloring matter. A suitable black color can be {411} made from the following materials: One part gelatin glue, 3 parts lampblack, aniline black, or a suitable quantity of logwood extract, 10 parts of glycerine, 1 part absolute alcohol, 2 parts water, 1 part Venetian soap, 1/5 part salicylic acid. For red, blue, or violet: One part gelatin glue, 2 parts aniline of desired color, 1 part absolute alcohol, 10 parts glycerine, I part Venetian soap, and 1/5 part salicylic acid.
The following are additional recipes used for this purpose: